The present invention relates to a chlorine-free multilayer film material, a process for its manufacture and its use for the manufacture of bags and pouches for ostomy/urostomy use.
Multilayer film materials having gas- and odour-barrier properties are well known and widely used in medical and food packaging industries.
These films comprise a core barrier layer which may contain chlorine or be chlorine-free. The chlorine-containing barrier resin most commonly employed is polyvinylidene chloride (PVDC), i.e. a copolymer of vinylidene chloride monomers with one or more ethylenically unsaturated comonomers copolymerizable therewith, such as vinyl chloride, alkylacrylates, alkyl methacrylates, acrylonitrile, etc. The barrier properties of PVDC are extremely high and are not deteriorated by the presence of moisture which in some applications is always present. However, PVDC presents a number of environmental disadvantages, especially relating to incineration of these materials after use.
It is well known in fact that PVDC is hazardous to the environment and to personal health. Upon incineration hydrochloric acid and potentially also polychlorinated dibenzodioxin and furan toxins are formed, which represent substantial environmental problems.
Chlorine-free barrier layers include vinyl alcohol comprising polymers, such as typically ethylene-vinyl alcohol (EVOH) copolymers and poly(vinyl alcohol) (PVAL), and--with lower barrier properties--polyamides, polyesters, polystyrenes.
While the barrier properties of the vinyl alcohol comprising polymers are very high under dry conditions, they are rapidly deteriorated in the presence of moisture.
In highly demanding applications, such as in the case of pouches for drainage of human body liquids, where the film is necessarily in contact with moisture but at the same time it is extremely important that the barrier layer retains its properties for as long as possible, barrier structures comprising a PVDC layer are widely appreciated in spite of the disadvantages indicated above. In particular the applicant company is currently manufacturing a film comprising a layer of PVDC sandwiched between opposing layers of EVA for use in the manufacture of ostomy pouches. Besides possessing high barrier properties, this structure also has mechanical properties (softness, quiteness, resistance) which render it particularly suitable for this application. Chlorine-free structures have been proposed also for these highly demanding applications but their performances are however far from those obtainable with PVDC-based structures.
Therefore, there exists a great need for a chlorine-free multilayer film structure for the manufacture of bags and pouches specifically for medical use, such as for the manufacture of ostomy/urostomy pouches, which combines the advantage of being chlorine-free with barrier properties to gases and odours as well as with overall mechanical properties as close as possible to those of PVDC-based structures.
DE-A-41 00 350 discloses a seven layer chlorine-free barrier packaging material for infusion solutions. The material comprises a base material consisting of a coextruded film made of an ethylene-vinyl alcohol copolymer and two coating polyethylene layers on both surfaces thereof, onto which a polyethylene layer and an ethyl-vinyl acetate copolymer layer are extrusion laminated.
EP-A-0 588 667 covers a multiple layer film useful in moisture barrier packaging applications, such as for the packaging of food products which require protection from the environment One preferred embodiment of said thermoplastic multi-layer film materials comprises a core layer made of an oxygen barrier material, such as an ethylene-vinyl alcohol copolymer, two intermediate layers provided on said core layer comprising a propylene polymer or copolymer or a polymeric adhesive, such as a carboxylic acid or maleic anhydride-modified polyolefin such as polypropylene-based carboxylic acid or maleic anhydride-modified polyolefin, moisture barrier layers comprising a blend of a propylene polymer or copolymer and a hydrocarbon resin and outermost layers covering the outer surfaces comprising propylene polymer or copolymer.
International patent application WO 93/11 938 relates to multilayered barrier structures for use in the manufacture of ostomy pouches. Said multilayered barrier structure comprises a five-layer material consisting of a gas barrier layer, two moisture barrier layers and optionally one or more adhesive layers disposed therebetween. The moisture barrier layer comprises a mesophase propylene-based material which contacts at least one of the sides of the non-chlorine gas barrier layer preferably made of an ethylene-vinyl alcohol copolymer. Said mesophase propylene-based material is stated to unexpectedly enhance the overall properties of the multilayered barrier structure.
Multilayer films comprising a gas and aroma barrier layer are disclosed as well in EP-B-0 1 18 060. The seven-layer composite film material comprises an inner barrier layer based on a saponified ethylene-vinylacetate copolymer, layers immediately adjacent to each of the two surfaces of said barrier layer comprising an adhesion promoting material of a modified polyolefin or a partially saponified ethylene-vinyl acetate copolymer on which a first layer made out of polypropylene or an ethylene-propylene copolymeris attached. which carries sealable outer layers made of an olefin homo- or copolymer. All the layers of the multilayered, dimensionally stable, sealable film are biaxially oriented with identical stretching ratios and heat-set.
U.S. Pat. Nos. 4,239,826 and 4,254,169 disclose multi-layer barrier films having a core gas barrier layer of a vinyl alcohol polymer or copolymer between opposing layers of a polyolefin blended with a chemically-modified polyolefin such as a vinyl acetate-vinyl alcohol copolymer, a vinyl alcohol-ethylene-vinyl acetate terpolymer or high density polyethylene with an unsaturated fused-ring carboxylic acid grafted thereto. The multi-layer barrier films of these documents are stated to be useful for the manufacture of containers in which foods are packaged.
DD-A-274 386 and DD-A-274 387 disclose coextruded composite films used for bags and pockets for human medicine, such as for ostomy bags, which comprise five layers and contain as the core gas barrier layer an ethylene-vinyl alcohol copolymer. Between the outer layers made of an ethylene-vinyl acetate copolymer and a blend of linear low density polyethylene and very low density polyethylene, respectively, and the core layer adhesive layers are inserted made of an ionomer resin.
5-layer chlorine-free ostomy pouches are already on the market. They share a core oxygen-barrier layer which comprises EVOH, two tie layers of modified ethylene-vinyl acetate copolymers on both sides of the core layer and two surface layers consisting of or comprising EVA.
While said multilayer films are free of chlorine and therefore satisfy the requirement of environmental safety, they are not fully satisfying as to their physical properties, specifically their oxygen permeability and moisture vapor transmission rate. As a matter of fact their oxygen permeability which is very low under dry conditions (0% relative humidity) increases remarkably at 100% relative humidity and becomes strikingly different from that of a PVDC-comprising structure of the same overall thickness.
Also the odour barrier properties of these structures seem to be very different from those of the PVDC-structures.
The problem to be solved by the present invention therefore is the provision of a chlorine-free multilayer film material having mechanical and odour barrier properties comparable with that of standard polyvinylidene chloride based multilayer film materials of the same thickness.
This problem is solved by the chlorine-free multilayer film material according to claim 1. The subclaims relate to preferred embodiments thereof, a process for the manufacture of said material and the use of this material for the manufacture of bags and pouches for ostomy/urostomy use.
The present invention therefore provides a chlorine-free filmmaterial comprising
a) a gas-barrier layer comprising a non-chlorine containing organic polymer which is substantially impermeable to oxygen gas; PA1 b) two tie layers each contacting one side of said barrier layer; PA1 c) an inner surface layer; PA1 d) an outer surface layer; and PA1 e) two intermediate layers positioned between said surface layers and said tie layers, comprising an ethylene-propylene copolymer having a flexural modulus (measured according to ASTM D-882) of less than 200 MPa. preferably less than 150 MPa.
A further subject matter of the present invention is a process for the manufacture of said chlorine-free multilayer film material comprising coextruding the materials for the gas-barrier layer, the two tie layers, the intermediate layers, the inner surface layer and the outer surface layer, cooling the coextruded film material, collapsing the cooled film material and optionally laminating a non-woven film to the multilayer film material obtained to the outer surface layer.
As used herein, the terms "polymer" or "polymer resin" generally include but are not limited to homopolymers, copolymers, such as, for instance, block, graft, random, and alternating copolymers, etc. as well as blends and modifications thereof.
The term "copolymer" is intended to denote polymers of two or more comonomers.